In the servicing and repair of motor vehicles, it is often necessary to remove and replace the engine. Although various types of hoist mechanisms have been developed for lifting an engine from the chassis or engine compartment, they have not been altogether satisfactory. Typically, engine hoists take the form of large, heavy duty equipment which is complicated and expensive. In addition, the engine hoist occupies a considerable amount of space which is a decided disadvantage in most applications where space is at a premium because of the many other types of equipment required in today's service departments.
Typical prior art compact hoists are described in Northern Hydraulics Catalog #113 (Northern Hydraulics Corp., 2800 Southcross Dr., Burnsville, Minn.) at page 101 (space saver engine hoist) and in U.S. Pat. No. 5,261,640 which issued on Nov. 16, 1993 to Francis Yuan. Other portable lifts and hoists are described in U.S. Pat. No. 5,375,963 (Wohlwend) and U.S. Pat. No. 5,188,247 (Jastrow).
While the hoists in the first two disclosures mentioned above are portable and can be compactly stored to some extent, they are difficult to reassemble for use and may require more than one person for hoist set up. Accordingly, it is one object of the present invention to provide a storable hoist that can be easily assembled and positioned for use by one person.
In prior art hoists of the above mentioned type, which are sometimes also called "space-saver" engine hoists, the hoist consists of a transverse base beam carried by a pair of support wheels with a pair of base legs extending therefrom which are likewise provided with support wheels. Removable base leg extensions are provided and the distal ends of these extensions are also provided with support wheels. The base also carries an upright post and lifting beam. With this arrangement there are three pairs of support wheels, each pair generally axially in a line with the lines parallel to each other. If all wheels are of the same diameter it was discovered that due to play in the leg extension connections the intermediate or middle pair became a principal load bearing pair of wheels or axis of rotation. Under load the rearward or base wheels tend to be lifted off the floor because of the turning moment transmitted through the lifting beam and post. To cure this instability, the middle pair of wheels or leg extension wheels were made with a smaller diameter than the other wheels so that the outermost four wheels were load bearing and the middle pair did not touch the floor. The drawback to this arrangement is that when the hoist is disassembled by removing the leg extensions for storage it is difficult for one person to remove the extensions or to later reconnect them because the hoist tilts forward and rests on the smaller diameter base leg wheels.
Accordingly, it is a principal object of the present invention to provide a stable hoist and a means and method by which one person can easily disassemble, store, and reassemble same.
Another problem encountered in using hydraulically operated prior art portable hoists is that in order to reach the operating position, that is, the extension of the beam to a point above the load being lifted a number of time consuming pump strokes are necessary. Accordingly, it is another object of the present invention to provide a means and method for manually and easily positioning and locking the lifting beam prior to applying hydraulic or mechanical pressure or lifting force.
The foregoing and other problems present in prior art hoists are solved or significantly reduced by the invention described in the summary below.